448 JAMES ERNEST KINDRED 



As in the younger stage the prootic processes abut against 

 the lateral surfaces of the trabeculae and are separated from them 

 by their perichondria (figs. 10, 11). Except for a greater size 

 of all parts concerned, the foramen for the passage of the ramus 

 hyomandibularis facialis and the jugular vein bears the same 

 relation to the trabeculae and prootic processes as in the 8-mm. 

 stage. In this region the trabeculae pass insensibly into the 

 parachordals. These immediately begin to thicken and are 

 fused laterally with the ventromesial walls of the otic capsules 

 (fig. 11). As the hypophysis tapers posteriorly the fenestra 

 hypophyseos begins to narrow and the parasphenoid lamella 

 dwindles to a mere spicule of bone forming its floor. WTiere the 

 hypophysis ends the anterior tip of the notochord appears 

 between the parachordals. It is enclosed in the fenestra basi- 

 cranii posterius. The roof of this fenestra is formed by fibrous 

 connective tissue confluent on each side with the dorsal peri- 

 chondria of the parachordals. The floor is formed by fibrous 

 connective tissue confluent with the ventral surface of the para- 

 chordals. The notochord is free and is not enclosed in cartilage 

 as is the intercranial notochord of the 6.6-mm. Gasterosteus. 

 The notochord is, however, much more closely applied to the 

 cartilage in Syngnathus than is the notochord of a 19-mm. 

 Amia. 



The parachordal-occipital process fusion in conjunction with 

 the posterior wall of the otic capsule forms as in the 8-mm. 

 stage, the canal for the passage of the glossopharyngeal and 

 vagus nerves. Ossification has not begun in this region. 



The postorbital process bears the same relation to the tri- 

 geminal ganglion that it did in the younger stage, but a deeper 

 notch occurs in the anterior margin of the prootic process poste- 

 rior to the ganglion (figs. 11, 13). This notch is the homologue 

 of the incisivum prooticum of Salmo. As in the younger Syng- 

 nathus the perichondria between the trabecula and the prootic 

 process persist. 



Due to the lateral growth of the brain and an increase in 

 size of the ramus hyomandibularis facialis and the jugular vein, 

 the foramen through which these pass is more ventral in the wall 



